System for injecting a liquid fuel into a combustion gas flow field

ABSTRACT

A system for injecting a liquid fuel into a combustion gas flow field includes an annular liner that defines a combustion gas flow path. The annular liner includes an inner wall, an outer wall and a fuel injector opening that extends through the inner wall and the outer wall. The system further includes a gas fuel injector that is coaxially aligned with the fuel injector opening. The gas fuel injector includes an upstream end and a downstream end. The downstream end terminates substantially adjacent to the inner wall. A dilution air passage is at least partially defined by the gas fuel injector. A liquid fuel injector extends partially through the dilution air passage. The liquid fuel injector includes an injection end that terminates upstream from the inner wall.

FIELD OF THE INVENTION

The present invention generally involves a system for supplying fuel toa combustor. In particular, the invention relates to a system forincreasing penetration of a axially staged liquid fuel into a combustiongas flow field.

BACKGROUND OF THE INVENTION

A gas turbine generally includes a compressor section, a combustionsection having a combustor and a turbine section. The compressor sectionprogressively increases the pressure of the working fluid to supply acompressed working fluid to the combustion section. The compressedworking fluid is routed through and/or around an axially extending fuelnozzle that extends within the combustor. A fuel is injected into theflow of the compressed working fluid to form a combustible mixture. Thecombustible mixture is burned within a combustion chamber to generatecombustion gases having a high temperature, pressure and velocity. Thecombustion gases flow through one or more liners or ducts that define ahot gas path into the turbine section. The combustion gases expand asthey flow through the turbine section to produce work. For example,expansion of the combustion gases in the turbine section may rotate ashaft connected to a generator to produce electricity.

The temperature of the combustion gases directly influences thethermodynamic efficiency, design margins, and resulting emissions of thecombustor. For example, higher combustion gas temperatures generallyimprove the thermodynamic efficiency of the combustor. However, highercombustion gas temperatures may increase the disassociation rate ofdiatomic nitrogen, thereby increasing the production of undesirableemissions such as oxides of nitrogen (NO_(X)) for a particular residencetime in the combustor. Conversely, a lower combustion gas temperatureassociated with reduced fuel flow and/or part load operation (turndown)generally reduces the chemical reaction rates of the combustion gases,thereby increasing the production of carbon monoxide (CO) and unburnedhydrocarbons (UHCs) for the same residence time in the combustor.

In order to balance overall emissions performance while optimizingthermal efficiency of the combustor, certain combustor designs includemultiple fuel injectors that are arranged around the liner andpositioned generally downstream from the primary combustion zone. Thefuel injectors generally extend radially through the liner to providefor fluid communication into the combustion gas flow field. This type ofsystem is commonly known in the art and/or the gas turbine industry asLate Lean Injection (LLI) and/or as axial fuel staging.

In operation, a portion of the compressed working fluid is routedthrough and/or around each of the fuel injectors and into the combustiongas flow field. A liquid or gaseous fuel from the fuel injectors isinjected into the flow of the compressed working fluid to provide a leanor air-rich combustible mixture which spontaneously combusts as it mixeswith the hot combustion gases, thereby increasing the firing temperatureof the combustor without producing a corresponding increase in theresidence time of the combustion gases inside the combustion chamber. Asa result, the overall thermodynamic efficiency of the combustor may beincreased without sacrificing overall emissions performance

One challenge with injecting a liquid fuel into the combustion gas flowfield using existing LLI or axial fuel staging systems is that themomentum of the combustion gases generally inhibits adequate radialpenetration of the liquid fuel into the combustion gas flow field. As aresult, local evaporation of the liquid fuel occurs along an inner wallof the liner at or near the fuel injection point, thereby resulting in ahigh temperature zone and high thermal stresses.

Current solutions to address this issue include extending at least aportion of the fuel injector radially inward through the liner and intothe combustion gas flow field. However, this approach creates a bluffbody in the combustion gas flow field that results in the formation of ahigh temperature recirculation zone downstream from the bluff body. Inaddition, this approach exposes the fuel injectors to the hot combustiongases which may impact the mechanical life of the component and lead tofuel coke buildup. Therefore, an improved system for injecting a liquidfuel into the combustion gas flow field for enhanced mixing would beuseful.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention are set forth below in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

One embodiment of the present invention is a system for injecting aliquid fuel into a combustion gas flow field. The system includes anannular liner that defines a combustion gas flow path. The annular linerincludes an inner wall, an outer wall and a fuel injector opening thatextends through the inner wall and the outer wall. The system furtherincludes a gas fuel injector that is coaxially aligned with the fuelinjector opening. The gas fuel injector includes an upstream end and adownstream end. The downstream end terminates substantially adjacent tothe inner wall. A dilution air passage is at least partially defined bythe gas fuel injector. A liquid fuel injector extends partially throughthe dilution air passage. The liquid fuel injector includes an injectionend that terminates upstream from the inner wall.

Another embodiment of the present invention is a system for injecting aliquid fuel into a combustion gas flow field. The system includes anannular liner that defines a combustion gas flow path within acombustor. The annular liner having an inner wall, an outer wall and afuel injector opening. The system further includes a fuel injector thatis coaxially aligned with the fuel injector opening. The fuel injectorcomprises an annular main body having an upstream end and a downstreamend. The annular main body defines a dilution air passage that providesfor fluid communication through the fuel injector into the combustiongas flow path. A gas fuel plenum is defined within the main body, and aliquid fuel plenum is defined within the main body. A plurality ofliquid fuel injectors extend from the main body into the dilution airpassage to provide for fluid communication between the liquid fuelplenum and the dilution air passage. The plurality of liquid fuelinjectors terminate upstream from the inner wall of the annular liner.

Another embodiment of the present invention includes a gas turbine. Thegas turbine includes a compressor and a combustor disposed downstreamfrom the compressor. The combustor includes an axially extending fuelnozzle that extends downstream from an end cover, a combustion gas flowpath defined downstream from the axially extending fuel nozzle and anannular liner that at least partially defines the combustion gas flowpath within the combustor. The annular liner includes an inner wall, anouter wall and a fuel injector opening. The gas turbine further includesa turbine that is disposed downstream from the combustor. The combustorfurther includes a system for injecting a liquid fuel into a combustiongas flow field that is defined within the combustor downstream from theaxially extending fuel nozzle. The system comprises a dilution airpassage that provides for fluid communication through the annular linerinto the combustion gas flow path, and a plurality of liquid fuelinjectors disposed within the dilution air passage, wherein the fuelinjectors terminate within the dilution air passage upstream from theinner wall of the annular liner.

Those of ordinary skill in the art will better appreciate the featuresand aspects of such embodiments, and others, upon review of thespecification.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof to one skilled in the art, is set forth moreparticularly in the remainder of the specification, including referenceto the accompanying figures, in which:

FIG. 1 is a functional block diagram of an exemplary gas turbine withinthe scope of the present invention;

FIG. 2 is a cross-section side view of a portion of an exemplary cantype combustor as may be incorporate various embodiments of the presentinvention;

FIG. 3 is a downstream perspective view of an annular liner according tovarious embodiments of the present invention;

FIG. 4 is a perspective view of a system for injecting a liquid fuelinto a combustion gas flow field, according to one embodiment of thepresent invention;

FIG. 5 is a cross section side view of a fuel injector and a portion ofan annular liner taken along line A-A as shown in FIG. 4, according toone embodiment of the present invention;

FIG. 6 is a bottom view of a fuel injector including a liquid fuelinjector and a portion of an annular liner according to variousembodiments;

FIG. 7 is a perspective side view of the system as shown in FIG. 4,according to another embodiment of the present invention;

FIG. 8 is a cross section side view of the system taken along sectionline B-B as shown in FIG. 7, according to one embodiment of the presentinvention;

FIG. 9 is a top view of a fuel injector and a portion of an annularliner as shown in FIG. 7, according to one embodiment of the presentinvention; and

FIG. 10 is a bottom view of the fuel injector and the portion of theliner as shown in FIG. 9.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to present embodiments of theinvention, one or more examples of which are illustrated in theaccompanying drawings. The detailed description uses numerical andletter designations to refer to features in the drawings. Like orsimilar designations in the drawings and description have been used torefer to like or similar parts of the invention. As used herein, theterms “first”, “second”, and “third” may be used interchangeably todistinguish one component from another and are not intended to signifylocation or importance of the individual components. The terms“upstream” and “downstream” refer to the relative direction with respectto fluid flow in a fluid pathway. For example, “upstream” refers to thedirection from which the fluid flows, and “downstream” refers to thedirection to which the fluid flows. The term “radially” refers to therelative direction that is substantially perpendicular to an axialcenterline of a particular component, and the term “axially” refers tothe relative direction that is substantially parallel to an axialcenterline of a particular component.

Each example is provided by way of explanation of the invention, notlimitation of the invention. In fact, it will be apparent to thoseskilled in the art that modifications and variations can be made in thepresent invention without departing from the scope or spirit thereof Forinstance, features illustrated or described as part of one embodimentmay be used on another embodiment to yield a still further embodiment.Thus, it is intended that the present invention covers suchmodifications and variations as come within the scope of the appendedclaims and their equivalents. Although exemplary embodiments of thepresent invention will be described generally in the context of acombustor incorporated into a gas turbine for purposes of illustration,one of ordinary skill in the art will readily appreciate thatembodiments of the present invention may be applied to any combustorincorporated into any turbomachine and is not limited to a gas turbinecombustor unless specifically recited in the claims.

Referring now to the drawings, wherein identical numerals indicate thesame elements throughout the figures, FIG. 1 provides a functional blockdiagram of an exemplary gas turbine 10 that may incorporate variousembodiments of the present invention. As shown, the gas turbine 10generally includes an inlet section 12 that may include a series offilters, cooling coils, moisture separators, and/or other devices topurify and otherwise condition a working fluid (e.g., air) 14 enteringthe gas turbine 10. The working fluid 14 flows to a compressor sectionwhere a compressor 16 progressively imparts kinetic energy to theworking fluid 14 to produce a compressed working fluid 18.

The compressed working fluid 18 is mixed with a fuel 20 from a fuelsupply system 22 to form a combustible mixture within one or morecombustors 24. The combustible mixture is burned to produce combustiongases 26 having a high temperature, pressure and velocity. Thecombustion gases 26 flow through a turbine 28 of a turbine section toproduce work. For example, the turbine 28 may be connected to a shaft 30so that rotation of the turbine 28 drives the compressor 16 to producethe compressed working fluid 18. Alternately or in addition, the shaft30 may connect the turbine 28 to a generator 32 for producingelectricity. Exhaust gases 34 from the turbine 28 flow through anexhaust section 36 that connects the turbine 28 to an exhaust stack 38downstream from the turbine 28. The exhaust section 36 may include, forexample, a heat recovery steam generator (not shown) for cleaning andextracting additional heat from the exhaust gases 34 prior to release tothe environment.

The combustors 24 may be any type of combustor known in the art, and thepresent invention is not limited to any particular combustor designunless specifically recited in the claims. For example, the combustor 24may be a can type or a can-annular type of combustor. FIG. 2 provides across-section side view of a portion of an exemplary gas turbine 10including a portion of the compressor 16 and an exemplary can typecombustor 24. As shown in FIG. 2, an outer casing 40 surrounds at leasta portion of the combustor 24. An end cover 42 is coupled to the outercasing 40 at one end of the combustor 24. The end cover 42 and the outercasing 40 generally define a high pressure plenum 44. The high pressureplenum 44 receives the compressed working fluid 18 from the compressor16.

At least one axially extending fuel nozzle 46 extends downstream fromthe end cover 42 within the outer casing 40. An annular liner 48 extendsdownstream from the axially extending fuel nozzle 46 within the outercasing 40. The annular liner 48 extends at least partially through thehigh pressure plenum 44 so as to at least partially define a combustiongas flow path 50 within the combustor 24 for routing the combustiongases 26 through the high pressure plenum 44 towards the turbine 28(FIG. 1).

The annular liner 48 may be a singular liner or may be divided intoseparate components. For example, the annular liner 48 may comprise of acombustion liner 52 that is disposed proximate to the axially extendingfuel nozzle 46 and a transition duct 54 that extends downstream from thecombustion liner 52. The transition duct 54 may be shaped so as toaccelerate the flow of the combustion gases 26 through the combustiongas flow path 50 just upstream from a stage of stationary nozzles (notshown) that are disposed proximate to an inlet of the turbine 28 withinthe combustion gas flow path 50. A combustion chamber 56 is defineddownstream from the axially extending fuel nozzle 46. The combustionchamber 56 may be at least partially defined by the annular liner 48. Asshown, the combustion gases 26 define a combustion gas flow field 58within the combustion gas flow path 50 downstream from the axiallyextending fuel nozzle 46.

FIG. 3 provides a downstream perspective view of the annular liner 48according to various embodiments of the present invention. As shown, theannular liner 48 generally includes an inner wall 60, an outer wall 62and a fuel injector opening 64 that extends through the inner wall 60and the outer wall 62. The fuel injector opening 64 provides for fluidcommunication through the annular liner 48. As shown, the annular liner48 may include multiple fuel injector openings 64 arrangedcircumferentially around the annular liner 48.

In particular embodiments, as shown in FIG. 2, the combustor 24 includesa system for injecting a liquid fuel into the combustion gas flow field58, herein referred to as “system 100”. The system generally includesthe annular liner 48 and at least one fuel injector 102 that providesfor fluid communication through the annular liner 48 and into thecombustion gas flow field 58. The fuel injector 102 may provide forfluid communication through the annular liner 48 including thecombustion liner 52 and the transition duct 54 at any point that isdownstream from the axially extending fuel nozzle 46.

FIG. 4 provides a perspective view of the system 100 including a portionof the annular liner 48 and the fuel injector 102 according to oneembodiment of the present invention. As shown, the fuel injector 102includes a gas fuel injector 104 and a liquid fuel injector 106. The gasfuel injector 104 may be fluidly coupled to a gas fuel source (notshown) and the liquid gas fuel injector may be fluidly coupled to aliquid fuel supply (not shown).

FIG. 5 provides a cross section side view of the fuel injector 102 and aportion of the annular liner 48 taken along line A-A as shown in FIG. 4,according to one embodiment of the present invention. As shown in FIG.5, at least a portion of the gas fuel injector 104 may be disposedwithin the fuel injector opening 64. In one embodiment, the gas fuelinjector 104 is coaxially aligned within the fuel injector opening 64with respect to a centerline of the fuel injector opening 64. The gasfuel injector 104 generally includes an annular main body 108. Theannular main body 108 includes an upstream end 110 and a downstream end112. In particular embodiments, the downstream end 112 terminatessubstantially adjacent to the inner wall 60 of the annular liner 48.

In particular embodiments, the annular main body 108 defines a dilutionair passage 114 that provides for fluid communication through the fuelinjector 102 and/or through the gas fuel injector 104 into thecombustion gas flow path 50. The upstream end 110 of the gas fuelinjector 104 may define an inlet 116 of the dilution air passage 114 andthe downstream end 112 may define an outlet 118 of the dilution airpassage 114.

In particular embodiments, the gas fuel injector 104 includes a gas fuelplenum 120 that is defined within the main body 108. As shown in FIG. 4,the gas fuel plenum 120 may extend circumferentially around the mainbody 108. In one embodiment, the gas fuel plenum 120 extendscircumferentially around the main body 108 generally proximate to theupstream end 110. One or more gas fuel ports 122 may provide for fluidcommunication between the gas fuel plenum 120 and the dilution airpassage 114.

In particular embodiments, as shown in FIG. 5, the liquid fuel injector106 extends partially through the dilution air passage 114. The liquidfuel injector 106 includes an injection end 124 that terminates adjacentto or upstream from the downstream end 112 and/or the outlet 118. Theinjection end 124 of the liquid fuel injector 106 is positioned outsideof the combustion gas flow path 50. In one embodiment, the injection end124 of the liquid fuel injector 106 terminates at a point that isbetween the inner wall 60 and the outer wall 62 of the annular liner 48.

FIG. 6 provides a bottom view of the fuel injector 102 including theliquid fuel injector 106, particularly the injection end 124 of theliquid fuel injector 106, and a portion of the annular liner 48according to various embodiments. As shown in FIG. 6, the liquid fuelinjector 106 may further comprise a plurality of liquid fuel injectionports 126 disposed across the injection end 124. In one embodiment, asshown in FIG. 6, the plurality of liquid fuel injection ports 126comprises a first liquid fuel injection port 128, a second liquid fuelinjection port 130 and a third liquid fuel injection port 132.

As shown in FIG. 6, the first liquid fuel injection port 128, the secondliquid fuel injection port 130 and the third liquid fuel injection port132 may be arranged in a triangular array across the injection end 124.In one embodiment, the first liquid fuel injection port 128 is spaced anequal distance 134 from the second liquid fuel injection port 130 andfrom the third liquid fuel injection port 132. In particularembodiments, the first liquid fuel injection port 128 is positionedupstream from the second liquid fuel injection port 130 and the thirdliquid fuel injection port 132 with respect to the direction of flow ofthe combustion gases 26 within the combustion gas flow path 50 (FIG. 5).

In operation, a portion of the compressed working fluid 18 (FIG. 2)flows through the dilution air passage 114 and into the combustion gasflow path 50. The liquid fuel is injected simultaneously within thedilution air passage 114 upstream from the inner wall 60 of the liner.As the compressed working fluid 18 interacts with the combustion gasflow field 58, a low velocity area is created within the combustion gasflow field 58. As a result, the liquid fuel penetrates deep within thecombustion gas flow field 58, thereby enhancing mixing with thecombustion gases before combustion. Local evaporation of the liquid fuelclose to the inner wall 60 of the annular liner 48 is substantiallyreduced, thereby reducing high temperature zones which are typicallycaused by the evaporated liquid fuel burning close to the inner wall 60.

The relative momentum between the liquid fuel and the compressed workingfluid 18 provides for the effective atomization of the liquid fuel. Thetriangular pattern and/or spacing of the first, second and third liquidinjection ports 128, 130, 132 in the injector end 124 creates threediscrete liquid fuel jets in a tripod fashion which enhances penetrationof the liquid fuel into the combustion gas flow field 58, therebycontributing to more complete mixing with the combustion gases. As aresult, net NOx production from fuel bound nitrogen is reduced. Theexact placement, size and number of liquid fuel injection ports 126 maybe optimized using various fluid dynamic analysis tools such ascomputational fluid dynamic (CFD) models.

In addition, by terminating the injection end 124 outside of thecombustion gas flow path 50, the liquid fuel injector 106 is shieldedfrom direct exposure to the combustion gases 26, thereby limitingthermal stress on the liquid fuel injector 106. In addition, bypositioning the liquid fuel injector 106 outside of the combustion gasflow path 50, undesirable flow patterns such as recirculation zones thatare normally associated with flow around a bluff body such as the liquidfuel injector 106 are eliminated at and/or downstream from the fuelinjector opening 64, thereby preventing potentially life limiting hotstreaks on the annular liner 48 in that area.

FIG. 7 provides a perspective side view of the system 100 according toanother embodiment of the present invention, and FIG. 8 provides a crosssection side view of the system 100 taken along section line B-B asshown in FIG. 7. In particular embodiments, as shown in FIG. 7, thesystem 100 includes the liner 48 and a fuel injector 150 that iscoaxially aligned with the fuel injector opening 64 (FIGS. 3 and 8). Asshown in FIGS. 7 and 8, the fuel injector 150 comprises an annular mainbody 152. As shown in FIG. 8, the annular main body 152 includes anupstream end 154 and a downstream end 156. The annular main body 150defines a dilution air passage 158 that provides for fluid communicationthrough the fuel injector 150 and into the combustion gas flow path 50.The upstream end 154 of the annular main body 152 defines an inlet 160of the dilution air passage 158 and the downstream end 156 defines anoutlet 162 of the dilution air passage 158.

A gas fuel plenum 164 is defined within the main body 152. In oneembodiment, a plurality of gas fuel ports 166 provide for fluidcommunication between the gas fuel plenum 158 and the dilution airpassage 158. In one embodiment, a liquid fuel plenum 168 is definedwithin the annular main body 152. The liquid fuel plenum 168 and/or thegas fuel plenum 164 may be in fluid communication with the fuel supply22 (FIG. 1).

FIG. 9 provides a top view of the fuel injector 150 and a portion of theliner 48 as shown in FIG. 7, according to one embodiment. FIG. 10provides a bottom view of the fuel injector 150 and a portion of theliner 48 as shown in FIG. 9. As shown in FIGS. 8, 9, and 10, a pluralityof liquid fuel injectors 170 extend from the annular main body 152 intothe dilution air passage 158 to provide for fluid communication betweenthe liquid fuel plenum 168 (FIG. 8) and the dilution air passage 158.

In particular embodiments, as shown in FIG. 8, the plurality of liquidfuel injectors 170 terminate upstream from the inner wall 60 of theannular liner 48 within the dilution air flow passage 158 and/orupstream from the downstream end 156 or outlet 162 of the annular mainbody 152 within the dilution air flow passage 158. In this manner, theplurality of liquid fuel injectors 170 are positioned outside of thecombustion gas flow path 50, thereby shielding the liquid fuel injectors170 from direct exposure to the combustion gases 26, thereby limitingthermal stress on the liquid fuel injectors 170. In addition, bypositioning the liquid fuel injectors 170 outside of the combustion gasflow path 50, undesirable flow patterns such as recirculation zones thatare normally associated with flow around a bluff body such as the liquidfuel injectors 170 are eliminated at and/or downstream from the fuelinjector opening 64, thereby preventing hot streaks on the annular liner48 and reducing thermal stress in that area.

In particular embodiments, as shown in FIG. 10, the plurality of liquidfuel injectors 170 comprises a first liquid fuel injector 172, a secondliquid fuel injector 174 and a third liquid fuel injector 176 that arearranged in a triangular array within the dilution air passage 158. Inone embodiment, the first liquid fuel injector 172 is positionedupstream from the second liquid fuel injector 174 and the third liquidfuel injector 176 with respect to the flow of combustion gases 26. Inone embodiment, the first liquid fuel injector 172 is spaced an equaldistance 178 from the second liquid fuel injector 174 and the thirdliquid fuel injector 176.

In operation, as illustrated in various FIGS., a portion of thecompressed working fluid 18 (FIG. 2) flows through the dilution airpassage 158 and into the combustion gas flow path 50. The liquid fuel isinjected simultaneously within the dilution air passage 158 upstreamfrom the inner wall 60 of the liner and/or the downstream end 156 oroutlet 162 of the annular main body 152. As the compressed working fluid18 interacts with the combustion gases 26, a low velocity area iscreated within the combustion gas flow field 58. As a result, the liquidfuel penetrates into combustion gas flow field 58, for example adistance equal to at least one diameter of the fuel injector opening 64,thereby enhancing mixing with the combustion gases before combustion.

Local evaporation of the liquid fuel close to the inner wall 60 of theannular liner 48 is substantially reduced, thereby reducing hightemperature zones which are typically caused by the liquid fuelevaporating and burning close to the inner wall 60. Relative momentumbetween the liquid fuel and the compressed working fluid 18 provides foreffective atomization of the liquid fuel. The triangular pattern and/orspacing of the first, second and third liquid fuel injectors 172, 174and 176 creates three discrete liquid fuel jets in a tripod fashionwhich enhances penetration of the liquid fuel into the combustion gasflow field 58, thereby contributing to more complete mixing with thecombustion gases. The exact placement, size and number of the liquidfuel injectors 170 may be optimized using various fluid dynamic analysistools such as computational fluid dynamic (CFD) models.

In addition, by terminating the liquid fuel injectors 170 outside of thecombustion gas flow path 50, the liquid fuel injectors 170 are shieldedfrom direct exposure to the combustion gases 26, thereby limitingthermal stress on the liquid fuel injectors 170. In addition, bypositioning the liquid fuel injectors 170 outside of the combustion gasflow path 50, undesirable flow patterns such as recirculation zones thatare normally associated with flow around a bluff body such as the liquidfuel injectors 170 are eliminated at and/or downstream from the fuelinjector opening 64, thereby preventing potentially life limiting hotstreaks on the annular liner 48 in that area.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal language of the claims.

What is claimed is:
 1. A system for injecting a liquid fuel into acombustion gas flow field, comprising: a. an annular liner that definesa combustion gas flow path, the annular liner having an inner wall, anouter wall and a fuel injector opening that extends through the innerwall and the outer wall; b. a gas fuel injector coaxially aligned withthe fuel injector opening, the gas fuel injector having an upstream endand a downstream end, wherein the downstream end terminatessubstantially adjacent to the inner wall; c. a dilution air passage atleast partially defined by the gas fuel injector, wherein the dilutionair passage provides for fluid communication through the annular linerinto the combustion gas flow path; and d. a liquid fuel injector thatextends partially through the dilution air passage, the liquid fuelinjector having an injection end that terminates upstream from the innerwall.
 2. The system as in claim 1, wherein the liquid fuel injectorfurther comprises a plurality of liquid fuel injection ports disposed atthe injection end.
 3. The system as in claim 1, wherein the liquid fuelinjector further comprises a first liquid fuel injection port, a secondliquid fuel injection port and a third liquid fuel injection portarranged in a triangular array across the injection end.
 4. The systemas in claim 3, wherein the first liquid fuel injection port is spaced anequal distance from the second liquid fuel injection port and from thethird liquid fuel injection port.
 5. The system as in claim 3, whereinthe first liquid fuel injection port is positioned upstream from thesecond liquid fuel injection port and the third liquid fuel injectionport with respect to a direction of flow of combustion gases within thecombustion gas flow path.
 6. The system as in claim 1, wherein theinjection end of the liquid fuel injector terminates between the innerwall and the outer wall of the annular liner.
 7. The system as in claim1, wherein the upstream end of the gas fuel injector defines an inlet ofthe dilution air passage and the downstream end defines an outlet of thedilution air passage.
 8. The system as in claim 1, wherein the gas fuelinjector comprises a gas fuel plenum that extends circumferentiallyaround the upstream end and a plurality of gas fuel ports that providefor fluid communication between the gas fuel plenum and the dilutionflow passage.
 9. A system for injecting a liquid fuel into a combustiongas flow field, comprising: a. an annular liner that defines acombustion gas flow path within the combustor, the annular liner havingan inner wall, an outer wall and a fuel injector opening; and b. a fuelinjector coaxially aligned with the fuel injector opening, the fuelinjector comprising: i. an annular main body having an upstream end anda downstream end, wherein the annular main body defines a dilution airpassage that provides for fluid communication through the fuel injectorinto the combustion gas flow path; ii. a gas fuel plenum defined withinthe main body; iii. a liquid fuel plenum defined within the main body;and iv. a plurality of liquid fuel injectors that extend from the mainbody into the dilution air passage to provide for fluid communicationbetween the liquid fuel plenum and the dilution air passage, wherein theplurality of liquid fuel injectors terminate upstream from the innerwall of the annular liner.
 10. The system as in claim 9, wherein theplurality of liquid fuel injectors comprises a first liquid fuelinjector, a second liquid fuel injector and a third liquid fuel injectorarranged in a triangular array within the dilution air passage.
 11. Thesystem as in claim 10, wherein the first liquid fuel injector ispositioned upstream from the second liquid fuel injector and the thirdliquid fuel injector with respect to a direction of flow of combustiongases within the combustion gas flow path.
 12. The system as in claim10, wherein the first liquid fuel injector, the second liquid fuelinjector and the third liquid fuel injector are arranged in a triangulararray within the dilution air passage.
 13. The system as in claim 10,wherein the first liquid fuel injector is spaced an equal distance fromthe second liquid fuel injector and the third liquid fuel injector. 14.A gas turbine, comprising: a. a compressor; b. a combustor disposeddownstream from the compressor, the combustor having an axiallyextending fuel nozzle that extends downstream from the end cover, acombustion gas flow path defined downstream from the axially extendingfuel nozzle and an annular liner that at least partially defines thecombustion gas flow path within the combustor, the annular liner havingan inner wall, an outer wall and a fuel injector opening; c. a turbinedisposed downstream from the combustor; and d. wherein the combustorfurther includes a system for injecting a liquid fuel into a combustiongas flow field within the combusor downstream from the axially extendingfuel nozzle, the system comprising: i. a dilution air passage thatprovides for fluid communication through the annular liner into thecombustion gas flow path; and ii. a plurality of liquid fuel injectorsdisposed within the dilution air passage, wherein the plurality ofliquid fuel injectors terminate within the dilution air passage upstreamfrom the inner wall of the annular liner.
 15. The gas turbine as inclaim 14, wherein the system comprises a gas fuel injector disposedcoaxially within the fuel injector opening, the gas fuel injector havingan upstream end and a downstream end, wherein the downstream endterminates substantially adjacent to the inner wall.
 16. The gas turbineas in claim 15, wherein the liquid fuel injector includes an injectionend that terminates adjacent to or upstream from the downstream end ofthe gas fuel injector.
 17. The gas turbine as in claim 14, wherein theliquid fuel injector further comprises a first liquid fuel injectionport, a second liquid fuel injection port and a third liquid fuelinjection port that are arranged in a triangular array across theinjection end, wherein the first liquid fuel injection port ispositioned upstream from the second liquid fuel injection port and thethird liquid fuel injection port with respect to a flow of combustiongases that flow through the combustion gas flow path.
 18. The gasturbine as in claim 18, wherein the system further comprises: a. anannular main body having an upstream end and a downstream end, whereinthe annular main body defines the dilution air passage; b. a gas fuelplenum that extends within the main body; c. a liquid fuel plenum thatextends within the main body; and d. wherein the at least one liquidfuel injector extends from the main body into the dilution air passageto provide for fluid communication between the liquid fuel plenum andthe dilution air passage.
 19. The gas turbine as in claim 18, whereinthe at least one liquid fuel injector comprises of a first liquid fuelinjector, a second liquid fuel injector and a third liquid fuel injectorarranged in a triangular array within the dilution air passage.
 20. Thegas turbine as in claim 18, wherein the first liquid fuel injector ispositioned upstream from the second liquid fuel injector and the thirdliquid fuel injector with respect to a flow of the combustion gases.